This invention relates to a differentials for vehicles and in particular to an improved structure for a vehicle differential which uses a rheological fluid to control the operation of the differential during use.
Differential gear mechanisms, commonly referred to as differentials, are well known devices which are used in the drive train systems of most vehicles. The differential is usually connected between an input driving shaft (typically a drive shaft assembly which is rotated by an engine of the vehicle) and a pair of output driven shafts (typically a pair of axles connected to the wheels of the vehicle). The differential is designed to distribute torque from the input shaft to the two output shafts, while permitting the two output shafts to rotate at different speeds under certain conditions. When the vehicle is operated in a straight line, the wheels of the vehicle turn at the same speed, and torque is distributed equally by the differential to the two wheels. When the vehicle negotiates a turn, the outside wheel rotates at a somewhat faster speed than the inside wheel. As a result, although torque is continued to be supplied to both wheels, a somewhat greater amount of torque is supplied to the inside wheel than to the outside wheel.
A conventional differential employs a number of meshing gears to accomplish the function described above. However, one of the drawbacks of conventional mechanical differentials is that when the vehicle is operated on a slippery surface, most or all of the torque will be distributed to a slipping wheel. For example, when one wheel of the vehicle is on a slippery surface, most or all of the torque will be delivered to that slipping wheel. As a result, the vehicle will become immobilized. To overcome this problem, it is known to provide mechanical differentials with additional mechanisms for limited or selectively preventing differentiation of speed between the two driven wheels. A number of such mechanically actuated limited slip and non-slip differential structures are known, most of which include a friction clutch structure of some type. Unfortunately, such structures are relatively complex and expensive in structure and operation. It would, therefore, be desirable to provide an improved structure for a differential which can be adjusted in accordance with the changing operating conditions of the vehicle.